The straightness of rod-like work pieces is a quality characteristic that may be of vital importance for the demands made on the work piece. In the past the straightness of a rod-like work piece, in particular that of a straightened pipe, was verified by visual judgement, which left the straightness measurement to the subjective perception of the person taking the measurement. Moreover, methods are known in which the straightness of a rod-like work piece was measured by way of mechanical scanning or through comparison with templates.
A method and a device for examining pipes is known from DE 10 2011 119 658 B4, in which the roundness and straightness of a pipe is checked using a non-contacting, optical method. The device comprises a support means for the pipe to be checked, and a portal that is arranged around the support means. The portal determines a portal plane that extends transverse to the longitudinal direction of the support means, wherein multiple optical roundness sensors are provided around the circumference of the portal, which are distributed in a transverse plane and are directed at the center of the portal, where said roundness sensors are used to take measurements of circumferential segments of the pipe. Moreover, the device comprises means with which the portal together with all sensors is moveable and adjustable transverse to the longitudinal direction of the support means in such a way, that the center of the portal coincides with the axis of the pipe in order to set and adjust the portal to a diameter of the pipe that may be between a smallest possible and a largest possible diameter. Moreover, means are provided to enable a controlled move relative to each other of the portal, including all optical sensors as well as the pipe resting on the support means, in longitudinal direction of the support means.
The devices and methods for determining the straightness of pipes known per se are elaborate and/or flawed due to the interaction with external forces or stresses respectively since the existing inherent stresses can lead to a distortion of the measuring result when placing the pipe onto a support means.